1. Field of the Invention
The present invention relates to a method and apparatus for controlling a User Equipment (UE) in a mobile communication system. More particularly, the present invention relates to a method and apparatus for controlling transmit power of a UE in a mobile communication system.
2. Description of the Related Art
Mobile communication systems were initially developed to provide a subscriber with a voice communication service while the user was on the move. With advances in communication technologies, the mobile communication systems have evolved to support high speed data communication services as well as the standard voice communication services.
The Long Term Evolution (LTE) standard, which is standardized by the 3rd Generation Partnership Project (3GPP), is an example of a next generation mobile communication system. The LTE standard is designed to provide for a downlink speed of up to 100 Mbps. In order to fulfill the requirements for an LTE system, studies have been done of various aspects including minimization of the number of involved nodes in the connections and placing the radio protocol closer to the radio channels.
Unlike the standard voice service, most data services are allocated resources according to the amount of data to be transmitted and according to a channel condition. Accordingly, in a wireless communication system such as a cellular communication system, it is important to manage resource allocation based on the resource scheduled for data transmission, the channel condition, and the amount of data to be transmitted. The importance of resource allocation management is also applicable in the LTE system. As such, in the LTE system, a base station scheduler manages and assigns radio resources based on the above considerations.
More recent studies have focused on the LTE-Advanced (LTE-A) standard, which improves the data rate with the adaptation of several new techniques. In the LTE-A system, the Specific Absorption Rate (SAR) requirement for controlling the influence of microwaves to the human body below a predetermined level is applied strictly. Accordingly, the UE's transmit power is limited to meet the SAR requirement. Furthermore, in order to prevent multiple communication modules from interfering with each other, it is also considered to reduce the UE transmit power for the LTE-A communication module. There is therefore a need of a method and apparatus for controlling a UE's transmit power efficiently in consideration of an uplink channel and a Hybrid Automatic Repeat reQuest (HARQ) process.